I should correct myself.
Tibetans use the words Vajrayana and Mantrayana as synonyms but AFAIK the former term doesn't appear in Kriya and Yoga Tantra because it's a later development, hence why East Asian Buddhists don't use it.

This is not correct.

The term "Vajrayāna" is found in yogatantra, in the Sarvatathāgatatattvasaṃgraha-nāma-mahāyāna-sūtra as well as the Vajra-śikhara-mahā-guhya-yoga-tantra It is also found in kriya tantra, in the Árya-avalokiteśvara-padmajāla-mūlatantrarāja-nāma and the Ārya-vajrakrodharājakalpa-laghutantra-nāma

In the Sarvatathāgatatattvasaṃgraha we find the term "Unsurpassed Vajrayāna."

The term "Vajrayāna" is found in yogatantra, in the Sarvatathāgatatattvasaṃgraha-nāma-mahāyāna-sūtra as well as the Vajra-śikhara-mahā-guhya-yoga-tantra It is also found in kriya tantra, in the Árya-avalokiteśvara-padmajāla-mūlatantrarāja-nāma and the Ārya-vajrakrodharājakalpa-laghutantra-nāma

In the Sarvatathāgatatattvasaṃgraha we find the term "Unsurpassed Vajrayāna."

Was awaiting your correction!
My mistake, in some Japanese and Indian academic texts it's presented the way I described earlier.
Thank you for the response.

Since sex is taught as the main core of tantric practice in the West and this does not benefit anyone, what is generally practiced as Tantra in the West is based on a big misunderstanding.

I think he is talking about 'New Age' Tantric sex and so on - which is what you would access in the West if you googled 'tantra'.

After observing this movement for 30 years, my conclusion is that Vajrayana is not really suitable for most people in both the West and in Asia, including Tibet.

in fact Shamar Rinpoche starts by saying Vajrayana is not suitable for most people on East and West! This must be in the context of his promotion of lojong in the period before his sudden death.

I would suggest that this is actually an attempt to put the tantras back into the category of 'secret' in the sense of being taught on a one-to-one or small group basis with tight personal samaya vows - rather than the public use of initiations bot in the West and East.

I should correct myself.
Tibetans use the words Vajrayana and Mantrayana as synonyms but AFAIK the former term doesn't appear in Kriya and Yoga Tantra because it's a later development, hence why East Asian Buddhists don't use it.
I think it's a case of Mantrayana being regarded as a subcategory of Vajrayana in later developments. Of course East Asian Mantrayana traditions would not recognize this categorization.

Also, Kalachakra was initially referred to as its own yana, Kalachakrayana, though considered a subcategory of Vajrayana.

It is my understanding that Kukai (774-835), who introduced Shingon to Japan, did use the term Kongōjō (aka vajrayana). A quick Google search of Abe's The Weaving of Mantra shows a few examples of this. FWIW